The disclosure relates to a device for injecting fuel into the combustion chamber of an internal combustion engine, having at least one injector, which has a high-pressure accumulator integrated into the injector body, an injection nozzle that has a nozzle needle which is guided in an axially movable manner and which is surrounded by a nozzle chamber, a high-pressure bore connecting the high-pressure accumulator and the nozzle chamber, and a feed bore for feeding high-pressure fuel to the high-pressure accumulator, wherein the feed bore has a lance connection arranged laterally on the injector body.
Injectors of this kind are used in modular common rail systems, which are characterized in that some of the reservoir volume present in the system is present in the injector itself. Modular common rail systems are used on particularly large engines, on which the individual injectors may under certain circumstances be fitted at considerable spacings. On such engines, using just a single rail for all the injectors is not expedient since there would be a massive dip in the injection pressure during injection owing to the long lines, with the result that there would be a significant drop in the injection rate in the case of a relatively long injection duration. On such engines, provision is therefore made to arrange a high-pressure accumulator within each injector. Such a design is referred to as a modular construction since each individual injector has a dedicated high-pressure accumulator and can thus be used as a self-contained module. Here, a high-pressure accumulator is not intended to mean a conventional line but is a pressure resistant vessel having an inlet and an outlet line, the diameter of which is significantly enlarged as compared with the high-pressure lines to enable a certain injection quantity to be dispensed from the high-pressure accumulator without an immediate pressure drop.
Injectors of modular common rail systems are fed with high-pressure fuel from a high-pressure pump, wherein the feed is accomplished either via a high-pressure connection of the injector on the top side of the high-pressure accumulator (“top feed”) or via a lance which makes lateral contact with the injector (“side feed”). In the case of the side feed, the lance opens via a lance connection of the injector into a feed bore, which opens into the high-pressure bore connecting the high-pressure accumulator to the nozzle pre-chamber. Fundamentally, the side feed has a number of advantages, especially in the case of large engines, since it allows the path of the fuel to the injector to be routed transversely through the cylinder, thereby generally making it possible to shorten the length of the feed as compared with a top feed. However, the conventional type of side feed is associated with the disadvantage that the high-pressure fuel flows directly from the lance connection to the injection nozzle during injection, leading to inadequate exchange of fuel in the high-pressure accumulator. However, exchange of the fuel is important to prevent deposits or the formation of residues. There is a risk of deposits or residues particularly with the use of high viscosity fuels, e.g. heavy oil in large diesel engines. Another disadvantage of the design described above involving side feed is that the outlet location of the feed bore into the high-pressure bore, which is usually embodied in the form of a T joint, is disadvantageous in terms of strength.